The strong indication is that, in highly developed economies, growth as measured by standard indices is of no real advantage to the people as a whole. (religion-online.org)
Note: they have lower liquidity than standard index ETFs, which means bigger bid / ask spreads, and this can be a real problem during times of low volatility. (lynalden.com)
(That's because PE is, indeed, «private» — there is no centralized reporting or standard index of returns.) (fortune.com)